Dr David Samson is working to unravel the evolutionary reasons behind our mismatched sleep patterns

Not everyone slips comfortably into what you might call 'normal' sleep patterns. Some of us are early risers who are happy to wake up before the birds, while there are others who stay up into the wee hours and can't be dragged out of bed in them morning.

Evolutionary biologist Dr David Samson from Duke University in North Carolina is working to unravel the reasons behind our mismatched sleep patterns and explained to Robbie Buck that it could all be down to helping us survive the dangers of the night.